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 Post subject: I2C Backpacks for Parallel LCDs
PostPosted: Thu Jan 21, 2016 12:48 pm 
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Guru

Joined: Fri Dec 07, 2012 3:48 pm
Posts: 67
Nowadays there are many cheap I2C backpacks available for parallel LCDs. These backpacks all use a PCF8574 I2C IO expander. I have three different brands of backpacks and they are all essentially the same, except some do not have the SDA and SCL pull-up resistors on board - like the HobbyKing "Arduino" I2C LCD backpacks. The most popular (and cheapest on Alliexpress.com) are exactly the same as the "SainSmart LCD2004".

These backpacks make the use of a parallel LCD really easy and convenient, just make sure that your LCD have connections in the same sequence as the backpack. Also, some LCDs have a Backlight current limiting resistor on board and some don't - Check. It is a MISSION to replace the backlight LED/s!!!

I have attached a sample program with different routines for writing different formats to an LCD. You will notice that I use REPEAT...UNTIL instead of FOR...NEXT because the REPEAT...UNTIL uses much less program memory.

There is a SUB in the program called "WRITE_LCD:", which you can modify to suit other hardware output methods (instead of the backpack), e.g. 74HC595, MCP23008, without having to change any of the other code. Just make sure that your connections and the "LCD_BUS_Data" Bits are the same.

I have also attached a schematic for the "LCD2004" backpack for those that like to poke around with a multimeter.


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LCD2004 I2C Backpack for Parallel LCDs.zip [77.39 KiB]
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 Post subject: Re: I2C Backpacks for Parallel LCDs
PostPosted: Mon Jan 25, 2016 12:53 pm 
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Site Admin
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Joined: Fri Apr 12, 2013 8:38 pm
Posts: 87
Location: Nottingham, England, UK
Thanks for that Andre

Very useful information and yet another great addition to the forum,

Dave
Basic Micro UK


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 Post subject: Re: I2C Backpacks for Parallel LCDs
PostPosted: Tue Jan 26, 2016 1:12 am 
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Master

Joined: Wed Oct 19, 2011 2:28 am
Posts: 123
Hi,
Just in case I used the following LCD display from Mouser part number :763-0420D3ZFLGBW-V3. It is a RS232 and used only one TTL output port. It is easy to use and best of it the used of one line to communicate. There are 2 lines and 4 lines display. They are pricey but the easy to programmed them it is will pay for the price.


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